1. Field of the Invention
The instant invention is directed to a class of 2-(tetrahydro-2-thienyl)phenols and carbamate derivatives thereof. More specifically, the instant invention is directed to a class of 2-(tetrahydro-2-thienyl)phenols useful as intermediates in the production of carbamate derivatives of 2-(tetrahydro-2-thienyl)phenols useful as insecticides.
2. Background of the Prior Art
The devastations caused by insects represent a serious economic threat to commercially important food, fiber and ornamental plants. Particularly serious is the attacks of insects against such important grain plants as corn and rice. For this reason the development of new, more effective insecticides represents an ongoing scientific activity. It is particularly important to develop insecticides effective at very low dosages. Such insecticides combine the necessary control of insects without attendant environmental difficulties.
The chemistry of reacting substituted phenols is known in the art. Gassman et al., J. Am. Chem. Soc., 100, 7611 (1978) describes methods for the ortho-formylation of phenols. Although a plurality of compounds are synthesized in accordance with the methods disclosed therein no 2-(tetrahydro-2-thienyl)phenols, with the exception of 2-methyl-6-(tetrahydro-2-thienyl)phenol, are disclosed therein. No utility for this compound, or for any of the other compounds synthesized in Gassman et al., is disclosed.
The utilization of aromatic substituted methyl or higher alkyl carbamates having insecticidal properties is well known in the art. One of the earliest of such disclosures in U.S. Pat. No. 2,903,478 which describes 1-naphthyl N-alkyl carbamates as having insecticidal properties against insect pests of fruits, vegetables, cotton and other plants.
U.S. Pat. Nos. 3,062,864, 3,062,865, 3,062,866, 3,062,867, and 3,062,868 disclose a group of N-methylcarbamates. The first four of these patents are N-methylcarbamates substituted with phenyl groups in which the phenyl substituted rings are themselves substituted in the meta position with alkyls. The substituted alkyls of the first four recited patents are, respectively, 1-methylbutyl, m-sec. butyl, 1-methylhexyl and 1-ethylpropyl. Each of these compounds are recited to have insecticidal properties. The last patent of this group, U.S. Pat. No. 3,062,868, discloses 3-t-amyl-6-bromophenyl N-methylcarbamate, also claimed to possess insecticidal properties.
Additional N-methylcarbamates useful as insecticides are set forth in U.S. Pat. No. 3,111,539. This patent teaches o-(2-isopropoxyphenyl)-N-methylcarbamate as well as o-(2-isopropoxyphenyl)-N,N-dimethylcarbamate.
U.S. Pat. No. 3,167,472 describes the insecticidal use of 3-methyl-5-(1-methylethyl)phenol esters of N-monomethyl and N,N-dimethyl carbamic acid.
Yet another disclosure of a carbamic acid ester having insecticidal properties is the disclosure in U.S. Pat. No. 3,336,186 which describes N,N-dialkyl-N-(3-(alkylamino)carbonyl)oxylphenylalkanimides. These compounds are said, in the U.S. Pat. No. 3,336,186, to possess pesticidal properties against mites.
Additional N-methylcarbamates having insecticidal properties includes 2-(1-methylpropyl)phenyl-N-methylcarbamate described by Metcalf et al., J. Econ. Entomol., 55, 889 (1962).
It is noted that all of the above phenyl N-substituted carbamates include no sulfur containing substituents. French Pat. No. 1,275,658 describes a nonsystemic insecticide which includes a sulfur-containing substituent on the phenyl substituent of the N-methyl carbamate. However, this is a multiple substituted phenyl group and the sulfur-containing compound is far removed from that of the present invention. German Offen. No. 1,910,588 describes 2-(ethylthiomethyl)phenyl-N-methylcarbamate as a systemic insecticide. This sulfur-containing compound is also far removed from the compounds of the present application.
Finally, U.S. Pat. No. 4,481,216 teaches control of corn rootworm by application of N-methyl 2-(1-methylethyl)phenylcarbamate.
Although the above references are directed to compounds used in the control of insects, there still is a continuing need for improved insecticides having specific application to commercially important plants but which can be utilized in very low dosage to minimize environmental side effects.